1. Field of the Invention
This invention relates to the field of processing systems, and in particular to a processor for use in a cryptographic system
2. Description of Related Art
The use of cryptography for encoding electronic content material continues to increase. In the entertainment field, digital audio and video recordings are encrypted to protect the material from unauthorized copying. In the communications field, documents are encrypted to prevent unauthorized viewing, and encrypted certificates are used to verify the authenticity of a document.
A number of standards have been adopted or proposed for encrypting copyright content material, or security items such as tickets that are associated with access to the copyright content material, each time the material is transferred from one device to another. For example, when a “compliant” CD-recorder creates a CD that contains a copy of copy-protected material, the recording will be cryptographically protected so that only a “compliant” CD-player will be able to render the material. “Compliant” devices are devices that enforce the adopted standard. If the original copy-protected content material has a “copy-once” copy limitation, the compliant CD-recorder will cryptographically mark the copy of this original with a “copy-never” notation. A compliant CD-recorder will recognize this “copy-never” notation and will not create a copy of this copy. If the material is copied by a non-compliant recorder, it will not contain the appropriate cryptographic item, and a compliant recorder or playback device will not record or render this copied material.
Standards have also been adopted for encrypting, signing, and authenticating transmitted content material, such as e-mail documents and attachments. The content material may be encrypted, and/or a cryptographically secure item may be attached to the content material that identifies the source of the content material. The secure item is attached, or “bound”, to the material in such a manner that a decryption of the secure item will identify whether the content material has been modified since it was originally transmitted.
The above examples of the increased use of encryption and decryption techniques, and in particular the increased use of cryptographic signing and verification and access ticketing, necessitates the inclusion of encrypting or decrypting devices in a variety of electronic devices. Every compliant audio or video recording or playback device, including both stationary and portable devices, must contain a means for processing or exchanging keys or other secure items, and generally must contain a cryptographic signing or verification device, or both. Every e-mail transmission or reception device, including multi-functioned devices such as cell-phones, will be expected to contain a signing or verification device, or both. Thus, a need exists for a processing device that facilitates cryptographic signing, verification, and key processing in a variety of systems.
Although a custom designed circuit may be the least costly embodiment of a device that implements an encryption or decryption process for digital signing, verification and other authentication tasks, the evolving nature of cryptography introduces the risk that the embodied algorithm will become obsolete. A general-purpose programmable processor will allow the embodied algorithm to change as cryptographic techniques change, but will not necessarily be economically feasible for inclusion in every device that requires cryptographic capabilities. A low-cost general-purpose processor may not achieve the performance goals expected on a real-time authentication process, for example, and auxiliary devices or a higher-speed processor may be required, at an increased cost. Even if the cost objectives can be met by a low-cost processor and auxiliary devices, the physical constraints of the containing system, such as a cell phone, may preclude the use of these auxiliary devices.